A New Image Cipher Using Chaotically Twisted Maps

Abstract

AbstractThis paper presents a new image encryption scheme that employs the Arnold cat map for total shuffling of the positions of image pixels and then uses two mixed chaotic maps twisted together to increase the key length and security. The states combination of two coupled chaotic systems are used to confuse the relationship between the plain-image and the cipher-image in a nonlinear fashion so as to resist against known plain-text and chosen plain-text attacks. In the diffusion process, the pixel values are altered sequentially. Various operations employed include nonlinear diffusion using the second chaotic key, random like diffusion of adjacent pixels and XORing with the third chaotic key. The security and performance of the proposed image encryption technique have been analyzed using statistical analysis, key sensitivity analysis, key space analysis, differential analysis and entropy analysis. The simulation shows that a single pixel difference of the plain-image will change almost all the pixels in the cipher-image (NPCR>99%), and the unified average changing intensity is high (UACI>33%). Since the entropy is found to be close to the theoretical value, we can observe that the information leakage is negligible and hence the scheme is highly secure. The experimental results demonstrate that the new algorithm has a low time complexity and the suggested encryption algorithm has the advantages of large key space and high security, and moreover, the distribution of grey values of the encrypted image has a random-like behavior.KeywordsTwisted Chaotic MapsPermutationByte SubstitutionNonlinear DiffusionRandom Diffusion